<?php
abstract class Xxtea{

    public static function encrypt($str, $key = XXTEA_KEY){
		$encode = base64_encode(self::_encode($str, $key));
		$encode = str_replace(array('+', '/', '='), array('_uaddu_', '_ugsadu_', '_e83ce_'), $encode);
        return $encode;
    }

    public static function decrypt($str, $key = XXTEA_KEY){
		$encode = str_replace(array('_uaddu_', '_ugsadu_', '_e83ce_'), array('+', '/', '='), $str);
        return self::_decode(base64_decode($encode), $key);
    }

    public static function xcrypt($str, $key = XXTEA_KEY){
		return md5($key . $str);
	}

	private static function _encode($str, $key){
        if($str == ''){
            return '';
        }
        $v = self::_str2long($str, true);
        $k = self::_str2long($key, false);
        if(count($k) < 4){
            for ($i = count($k); $i < 4; $i ++) {
                $k[$i] = 0;
            }
        }
        $n = count($v) - 1;
        $z = $v[$n];
        $y = $v[0];
        $delta = 0x9E3779B9;
        $q = floor(6 + 52 / ($n + 1));
        $sum = 0;
        while(0 < $q--){
            $sum = self::_int32($sum + $delta);
            $e = $sum >> 2 & 3;
            for($p = 0; $p < $n; $p++){
                $y = $v[$p + 1];
                $mx = self::_int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::_int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
                $z = $v[$p] = self::_int32($v[$p] + $mx);
            }
            $y = $v[0];
            $mx = self::_int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::_int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
            $z = $v[$n] = self::_int32($v[$n] + $mx);
        }
        return self::_long2str($v, false);
    }

    private static function _decode($str, $key){
        if ($str == ''){
            return '';
        }
        $v = self::_str2long($str, false);
        $k = self::_str2long($key, false);
        if(count($k) < 4){
            for($i = count($k); $i < 4; $i ++){
                $k[$i] = 0;
            }
        }
        $n = count($v) - 1;
        $z = $v[$n];
        $y = $v[0];
        $delta = 0x9E3779B9;
        $q = floor(6 + 52 / ($n + 1));
        $sum = self::_int32($q * $delta);
        while($sum != 0){
            $e = $sum >> 2 & 3;
            for($p = $n; $p > 0; $p--){
                $z = $v[$p - 1];
                $mx = self::_int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::_int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
                $y = $v[$p] = self::_int32($v[$p] - $mx);
            }
            $z = $v[$n];
            $mx = self::_int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ self::_int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
            $y = $v[0] = self::_int32($v[0] - $mx);
            $sum = self::_int32($sum - $delta);
        }
        return self::_long2str($v, true);
    }

    private static function _long2str($v, $w){
        $len = count($v);
        $n = ($len - 1) << 2;
        if($w){
            $m = $v[$len - 1];
            if (($m < $n - 3) || ($m > $n))
                return false;
            $n = $m;
        }
        $s = array();
        for($i = 0; $i < $len; $i ++){
            $s[$i] = pack("V", $v[$i]);
        }
        if($w){
            return substr(join('', $s), 0, $n);
        }else{
            return join('', $s);
        }
    }

    private static function _str2long($s, $w){
        $v = unpack("V*", $s . str_repeat("\0", (4 - strlen($s) % 4) & 3));
        $v = array_values($v);
        if($w){
            $v[count($v)] = strlen($s);
        }
        return $v;
    }

    private static function _int32($n){
        while($n >= 2147483648){
            $n -= 4294967296;
        }
        while($n <= -2147483649){
            $n += 4294967296;
        }
        return (int)$n;
    }

}
